Not Applicable
Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates generally to phase logic devices and relates specifically to logic gates operating with no active components and performing logic primarily using the phase of a signal.
2. Discussion of Related Art
The field of optics is expanding at a phenomenal rate. Many types of devices for controlling optic signals have been developed. Optical devices are replacing a variety of electronic functions and optical logic gates are one of the most important areas of development in optical computing.
Logic gates using a combination of electronics and optics have been developed; however, these devices are limited in speed by the electrical-optical interaction. All-optical logic devices are preferable because they are capable of much higher operating speeds.
A variety of physical phenomena has been exploited to create all-optical logic gates, but phase effects and beam interference have provided some of the simplest and fastest methods yet.
Several phase logic devices exist; however, they require feedback or special filtering to operate. They also have not taken advantage of the simple optic components that are currently available.
In U.S. Pat. No. 5,555,126, Hait describes a special phase interference technique that transmits all input energy to an output signal. He also describes an AND phase logic gate that requires a feedback signal. The feedback signal adds extra transmission time to the phase logic gate and creates a more complex operation. He also does not describe how the phase logic gate can be made from available technology and components.
In U.S. patent application Ser. No. 09/522,912, assigned to the assignee of the present application, a special filtering method that uses a threshold device is described. A phase logic device that employs the special threshold filtering method is also described. However, threshold devices are special optical components that have not yet been developed to full economic viability on a mass production scale.
A simple and versatile phase logic device that uses commonly available and easily manufacturable components would be economically viable immediately and is needed to further advance the optical computing cause.
It is, therefore, an object of the present invention to provide a logic device that fulfills the above mentioned deficiencies.
A coupler-based programmable phase logic device is a phase logic device that is composed of signal combiners. The device can be used with any coherent signals, in particular, optic beams, such as laser beams, or microwave signals, such as maser beams. The device uses only 3-port couplers and 4-port couplers. Control input signals determine the logic function performed by the device and can be changed dynamically for dynamic and programmable device operation.
The device receives two coherent data input signals and three coherent control input signals and produces a coherent phase modulated data output signal. The two data input signals are externally phase modulated to have one of two phase values, as in the binary phase shift keying method. The data output signal is a phase modulated signal having one of the two phase values that is related to the phase values of the data input signals by a Boolean logic function, such as AND or OR.
The device is composed of a mixing stage and a logic stage. The data input signals are directed into a mixing stage which produces two intermediate signals. The intermediate signals are then directed into the logic stage which produces the data output signal.
The mixing stage consists of a cross-over section and a transferring section. The cross-over section facilitates an interaction between the data input signals and the transferring section applies two control input signals.
The logic stage consists of a combining section and a magnitude shifting section. The combining section combines the intermediate signals, and the magnitude shifting section modifies the magnitude of the data output signal with a third control input signal.